Lake Winnipeg Regulation water levels

In 1970, Manitoba Hydro was granted its first Interim Licence to regulate Lake Winnipeg. When the lake's level is between 216.7 metres (711 ft.) and 217.9 metres (715 ft.) above sea level (ASL), the licence allows Manitoba Hydro to set the outflows as required for power production purposes along the Nelson River. In December 2010, Manitoba Hydro applied for a final licence.

Sometimes the lake level will rise above or drop below these levels, such as during high or low runoff periods. Under such extremes, the lake will be operated to return to the licensed operating range as quickly as inflow conditions will permit.

During times of high inflow, when the level of the lake rises above an elevation of 217.9 metres ASL, Manitoba Hydro must maintain maximum outflow in order to return the level of the lake to below 217.9 m as soon as possible.

During drought periods, the level of the lake may fall below 216.7 m ASL. If this should occur, outflows from the lake are determined by the Minister of Conservation.

Common misconceptions

Since the Lake Winnipeg Regulation (LWR) project was built, the level of the lake throughout the annual cycle is similar to the pre-regulation period – the lake rises in the spring with the spring freshet, peaks in the summer, and falls throughout the fall and winter. The average level of the lake has remained virtually the same as the average level prior to regulation:

Prior to 1976, the average level of the lake was 713.4 feet above sea level.

Average level since regulation began is 713.6 feet.

In addition, the wide fluctuations between the highest and lowest levels have been substantially reduced. Because of the project, the risk of devastating high water levels, such as those that occurred in 1966 and 1974, has been reduced. As well, regulation can protect against extreme low levels that would naturally occur in dry years such as in 1932, 1941 and 1962.

Weather conditions, such as wind and barometric pressure, can cause levels to differ substantially at various points on the lake. Manitoba Hydro uses the daily average level readings from 8 federal water level gauges to determine the lake's level. These gauges are located at:

Misconception #2: Manitoba Hydro keeps water levels in the fall months higher than would be the case in an unregulated state.

Records show that the daily average water levels after 1976 are similar to the daily average levels prior to regulation, including in the fall months. There is no need to keep higher water levels because:

The deeper channels built for Lake Winnipeg Regulation (LWR) were designed to overcome freezing and ice-blocking, enabling Manitoba Hydro to discharge more water out of the lake through the winter (for electricity production) than would have been possible for the same starting levels without LWR.

Our strong export tie-lines (transmission lines) to neighbouring electricity markets enhance reliability and energy security for Manitobans. We can release water from the lake in the summer and sell the extra electricity produced to our customers in the US (who use it for air conditioning) and buy it back in the winter, if we need to.

Our control facility at Jenpeg, along with the associated channels, allows us to ensure sufficient water remains in the lake in average or low water years to sustain a reliable supply of electricity production from northern hydro plants in almost all years.

Misconception #3: A lower maximum water level would eliminate erosion of lakefront properties.

A maximum level of 714 feet, as has been suggested by some, would not likely assist with property damage issues in any significant way because the main driver for shoreline erosion is wind events. Influencing factors on water levels.

A permanent lower limit for power productions would have little or no impact on erosion and property damage on Lake Winnipeg. However, a lower limit would:

increase flooding events and impacts to over 15,000 people living in communities downstream of Lake Winnipeg;

cost us, and in turn our customers (rate payers), many millions of dollars in lost energy production;

have environmental impacts on Lake Winnipeg through lowering of the long-term average of the lake.